Obstructive sleep apnea (OSA) is a common disease that carries significant risks for cardiovascular disease, mortality, and economic costs. Almost thirty years ago, initial population studies found the prevalence of OSA to be five to nine percent of the adult population. Excess body weight is a risk factor for the development of OSA, and the recent rise in prevalence of obesity has led to revised estimates of OSA prevalence, now at seventeen percent of the adult population. OSA is poorly recognized clinically; currently 85% of apneics remain undiagnosed and untreated.
OSA derives fundamentally from structural abnormalities of the pharynx that cause pharyngeal narrowing or closure during sleep and produce recurrent apneas and hyponeas. During wakefulness, compensatory neuro-muscular reflexes protect the pharynx from collapse. These reflexes are lost during sleep, leaving the collapsible human pharynx susceptible to narrowing or closure. Nasal continuous positive airway pressure (CPAP), comprised of an air generator and nose mask, is the standard therapy for OSA. CPAP delivers positive pressure to the pharyngeal lumen, thereby dilating it and eliminating obstruction. While CPAP therapy is highly efficacious, it is cumbersome and its effectiveness is compromised by a relatively low adherence rate. Adherence depends on the methods used to initiate therapy and on the severity of OSA, being higher in subjects with more severe hypoxemia and excessive daytime sleepiness. In current practice, CPAP therapy adherence rate appears to approximate fifty percent.
The only currently available alternative to CPAP is oral appliance (OA) therapy. Oral appliances maintain patency of the airway during sleep by stabilizing and protruding the mandible and/or the tongue. The most commonly used type of OA is a custom-made mandibular repositioner (MR) which protrudes the mandible. Mandibular protrusion in paralyzed subjects dilates both the velopharynx and the oropharynx. In clinical practice, a specialist dentist fabricates a custom-fitted OA covering upper and lower teeth. The appliance is then empirically adjusted to progressively protrude the mandible until a therapeutic end-point is reached. MR therapy is better accepted by the OSA subject than nasal CPAP therapy, and self-reported adherence rates are high. Unfortunately, MR therapy is not uniformly effective in OSA. Reported effectiveness ranges from 50 to 65 percent, and a recent study found 50 percent success rate.
Because of the uncertainties regarding use of MR therapy for treating OSA, current practices focus primarily on the use of nasal CPAP therapy. Virtually all subjects found to have OSA receive a trial of nasal CPAP. If the subjects prove non-adherent with CPAP therapy, the subjects may then be offered MR therapy. The American Academy of Sleep Medicine recommends MR therapy as a CPAP therapy alternative in subjects with OSA of mild to moderate severity. However, lacking a valid test for clinically selecting subjects with OSA who will have a favorable response to MR therapy, reimbursement for MR therapy is usually provided only for apneics who fail CPAP therapy.